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The yellow colour is due to xanthoproteic acid which is formed due to nitration of certain amino acids, most common examples being tyrosine and tryptophan. [1] This chemical reaction is a qualitative test, determining the presence or absence of proteins. Reaction of nitration of tyrosine as an example of the xanthoproteic reaction
In addition to the common amino acid L-tyrosine, which is the para isomer (para-tyr, p-tyr or 4-hydroxyphenylalanine), there are two additional regioisomers, namely meta-tyrosine (also known as 3-hydroxyphenylalanine, L-m-tyrosine, and m-tyr) and ortho-tyrosine (o-tyr or 2-hydroxyphenylalanine), that occur in nature.
The reagent is made by dissolving metallic mercury in nitric acid and diluting with water, forming mercuric nitrate (Hg[NO 3] 2). [3] In the test, the phenol group in the side chain of tyrosine gets nitrated, and that product then complexes with Hg(I) or Hg(II) ions to give a red colored precipitate.
Nitrosation and nitrosylation are two names for the process of converting organic compounds or metal complexes [1] into nitroso derivatives, i.e., compounds containing the R−NO functionality. The synonymy arises because the R-NO functionality can be interpreted two different ways, depending on the physico-chemical environment:
Sodium nitrate is also synthesized industrially by neutralizing nitric acid with sodium carbonate or sodium bicarbonate: 2 HNO 3 + Na 2 CO 3 → 2 NaNO 3 + H 2 O + CO 2 HNO 3 + NaHCO 3 → NaNO 3 + H 2 O + CO 2. or also by neutralizing it with sodium hydroxide (however, this reaction is very exothermic): HNO 3 + NaOH → NaNO 3 + H 2 O. or by ...
C + 2 H 2 SO 4 → CO 2 + 2 SO 2 + 2 H 2 O S + 2 H 2 SO 4 → 3 SO 2 + 2 H 2 O. Catalysts like selenium, Hg 2 SO 4 or CuSO 4 are often added to make the digestion go faster. Na 2 SO 4 or K 2 SO 4 is also added to increase the boiling point of H 2 SO 4. Digestion is complete when the liquor clarifies with the release of fumes. [3] A distillation ...
[1] [2] Azlactone chemistry: step 2 is a Perkin variation. Hippuric acid, the benzamide derivative of glycine, cyclizes in the presence of acetic anhydride, condensing to give 2-phenyl-oxazolone. [3] This intermediate also has two acidic protons and reacts with benzaldehyde, acetic anhydride and sodium acetate to a so-called azlactone.
The enzyme tyrosine phenol-lyase (EC 4.1.99.2) catalyzes the chemical reaction L -tyrosine + H 2 O ⇌ {\displaystyle \rightleftharpoons } phenol + pyruvate + NH 3 This enzyme belongs to the family of lyases , specifically in the "catch-all" class of carbon-carbon lyases.